As an information output apparatus, for example in a word processor, a personal computer, a facsimile machine or the like, printers for recording information, such as characters and images, on a sheet type recording medium such as printing paper or a film, have been broadly used.
As a typical liquid (ink) discharging type in recording heads mounted on inkjet recording apparatuses, a type using an electromechanical transducer such as a piezoelectric device, and a type using thermal energy are known. Inkjet recording heads have been put broadly into practical use, which heat liquid by an electrothermal conversion element (heater) and allow droplets to be discharged by an operation of film boiling. The configuration is such that an electrothermal conversion element is disposed within an ink chamber, and an electric pulse acting as a recording signal is supplied to this element to heat it, whereby thermal energy is supplied to the liquid. Then, by utilizing bubble pressure of liquid caused by a phase change of liquid when bubbled, very small droplets are discharged from a tiny discharge aperture (nozzle) to perform recording on a recording medium.
Further, there is another type recording system as an improved type for the above-mentioned type, wherein ink droplets are made uniformly by communicating bubbles with air, and discharge of minute droplets are performed. According to this type of recording, it becomes possible to secure a stable discharge amount of such minute ink droplets and to attain a high quality printing.
A recording apparatus provided with the above described inkjet recording head uses in addition to black ink being monochrome type ink liquid, color type ink liquids (inks) of cyan, magenta and yellow, and is provided with recording heads of the above described type, each corresponding to the kind of ink used.
Generally, due to the trend toward high image quality, the number of discharge apertures of each recording head section has increased to 64-128, and further to 256 or the like; there has been provided a high density arrangement such as 300 dpi or 600 dpi in a unit of “dpi” indicating the number of discharge apertures per inch. The heating element (heater) acting as an electrothermal transducer disposed in these discharge apertures is driven by a high-frequency pulse on the order of several μsec to 10 μsec to form bubbles by film boiling, thereby implementing a high-rate, high-image-quality printing.
To achieve a high-definition color recording equivalent to silver halide photography, the size of dots must be reduced to the extent that the dots cannot be recognized (do not appear granular) on the printing paper. In this case, a setting is made such that the color ink droplet is approximately 5 pl (picoliter is a 10−12 liter), 40 to 50 μm in dot diameter, and 600×1200 to 1200×1200 dpi (dpi being a unit indicating the number of dots per inch). The above described atmosphere communication system printers are substantially compatible with such setting.
Means for electrically connecting the above described recording head and a recording apparatus is disposed in a carriage which allows the recording head mounted thereon to perform back and forth scanning. Specifically, the carriage is provided with a plurality of contacts, and when the recording head is attached to the carriage, a connection with a plurality of contacts provided in the recording head side is made, whereby an electrical connection between the recording head and the inkjet recording apparatus is achieved.
Japanese Patent Laid-Open No. 8-252909 (U.S. Pat. No. 5,828,386) discloses a recording head and a recording apparatus provided with a configuration for monitoring this electrical connection status. An AND circuit calculating a logical product between a recording signal supplied from the recording apparatus to an input terminal of the recording head, a clock signal for transferring the recording signal and a control signal for recording operation by the recording signal, and an output terminal for outputting the calculation result are provided in the recording head. Accordingly, it is possible to prevent recording failure such as recording dot dropouts, and damage etc. of recording head induced by the defective contact. Accordingly, such confirmation and/or monitoring of connection status becomes important, particularly in a recording head integrated with an ink tank and being detachable to an inkjet recording apparatus.